The present invention disclosed herein relates to a method of manufacturing a thermoelectric material, a thermoelectric material prepared by the method, and a thermoelectric generator using the same.
Due to great demands for electricity all over the world, sustainable energy technologies have attracted great attention. However, renewable energy sources, such as solar power, wind power or the like are in charge of only an extremely small proportion of total electricity generation due to relatively high costs. In this regard, heat energy has been evaluated as having a low cost, sustainable and potential energy source. However, a significant proportion of the energy is wasted in the form of heat. Heating processes in households, exhausts in vehicles, and industrial processes all generate a significant amount of waste heat. Due to such a large potential, there is a lot of interest in a cost-effective technology for generating electricity from the waste heat.
In relation to this, since a thermoelectric material is capable of directly converting heat into electricity, the thermoelectric material has attracted much more attention. The thermoelectric material is a metal or ceramic material having a function capable of directly converting heat to electricity, or electricity into heat, and applications of the thermoelectric material to a thermoelectric generation or thermoelectric cooling using waste heat generated by waste incineration, waste heat generated by a turbine generation, exhaust gas heat of vehicle, waste heat generated by combustion of city gas, various industrial waste heat and the like have attracted attention. The thermoelectric generation using such thermoelectric materials has a characteristic in that power generation is possible without a separate operation unit if only a difference in temperature is given, and has advantages in which a structure thereof is simple and a breakdown thereof is rare, so that maintenance and management are easy, a noise is negligible, and a selection range of a used heat source is wide. Also, the thermoelectric cooling has characteristics and advantages in that a breakdown thereof is rare, a noise is negligible, selective cooling for micro portions is possible, and thermal response sensitivity is high, so that a precise heat control is possible, and a compressor or refrigerant is not necessary.
Meanwhile, efficiency of the thermoelectric material may be evaluated as a performance index ZT=S2T/ρκ, where S is a Seebeck coefficient, ρ is electric resistance, κ is heat conductivity, and T is absolute temperature. That is, as the more the performance index, the higher the conversion efficiency is.
Since an amount of electric energy in thermoelectric materials increases in proportional to the performance index, a thermoelectric material having a high performance index represents an excellent property. Therefore, for an application of a material to the thermoelectric material from the above formula, there is required a thermoelectric material having high Seebeck index, high electrical conductivity, and low thermal conductivity.
While a PbTe-based alloy that is one of typical thermoelectric materials has been studied for a long time, the performance index stays close to about 1 for decades. Recently, a new physical principle capable of improving the thermoelectric performance has been proposed, but the improvement of the performance index is limited.